Why did the ameeicans lose in the Vietnam war?

Answer 1

Because there was no clear definition of the objective in being in Vietnam in the first place, hence there was no way to succeed. Lacking this definition also meant lack of public support.

The same exact thing has happened in Iraq.

Answer 2

Geography of the war zone & the Communist Super Powers were the reasons for the failure. 1. Had South Vietnam been a peninsula, as Korea is, we could have isolated the enemies re-supply of men & material; as we did during the Korean War. 2. If the Communist Super Powers did NOT exist; we could have gone into Laos and Cambodia with immunity; and destroyed or occupied the Ho Chi Minh Trail, or any other road network the enemy used. As things stood: We couldn't stop the flow of men & material; and could not risk involving any of the communist super powers. We had taken that risk during the Korean War, and ended up fighting Red China, as well as North Korea; we weren't about to repeat our mistakes.